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Engine basics => Engine set up tips => Topic started by: Larry Wong on October 22, 2008, 05:44:52 PM
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OK this new to me
, It just started in the last 3 or 4 times. What happens is when I fill the tank on my P/A 61 plane with inverted engine, and plane is right side up , I fill the tank getting ready for my turn to fly, when it's my turn , the engine is loaded up with fuel (flooded) I turn the plane inverted back flip a few times to clear the fuel out, and it starts right up! now with an inverted engine I woild think that even if the fuel expands in tank it would just flow out the venturi...Any Ideas???? HB~> HB~> HB~> HB~>
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Larry,
If you have an air ram for tank pressurization, you should be plugging the ram with a piece of plugged tubbing or just leaving your fuel syringe connected while waiting. This will maintain a vaccum on the system till you remove the plug or syringe. Hope this helps. :)
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Thanks James
I'll give it a try, Or turn the plane around... hee -hee ! LL~ LL~
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Is fuel running back through the pressure line into the muffler/pipe and getting through the exhaust port?
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the engine is a P/A 61 R E with pipe and a uniflow tank with vent pressure, engine is mounted inverted and when it is fueled the venturi is pointed down, so if in fueling it would run down and out, not up to crank shaft then cyclinder to flood.
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My guess is it's getting flooded when you fill it.. Try turning the prop backwards against compression to close off the intake port then any excess will simply run out the venturi...
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I've got a model like that too. ST46 with unflow venting, no pressure. Always tanked up with the prop turned back against compression.
I always leave my filling syringe attached until I'm ready to move to the flight line with this model.
One other thing I did was to replace the fuel line with narrower bore. I can't see why the narrower bore tubing would do anything positive - other than better seal around the feed pipe from the tank, but the combination of the narrower bore tube and the syringe remaining attached sems to fix the problem for me
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When your plane is sitting on it's wheels where is your uniflow vent exiting the tank. If it is not at the top it will allow fuel to flow into the muffler if you are using muffler pressure. Also is the vent above the tank on the out side of the body for the same reason. When I build tanks I bend the uniflow vent to the bottom and then exit near the top front that way no fuel can run out even when the plane is turned over to start it.. Sounds to me like it is happening when you fill it.Remember the needle valve hole is facing the crank opening and there is a lot of pressure to force fuel in. Do as some have said turn prop back against compression to fill tank.
Your problem is very common and I see it all the time at contest.
Ed
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Often if the tank is filled in the pits and then carried to the circle the plane is allowed to get in a nose down attitude and gravity allows the fuel to run out. This has the potential to flood the motor although you would think that most of the fuel would run out the venturi.
The amount of fuel for a correct prime and flooding is not that much depending on the motor.
Busby